1. Field of the Invention
The present invention relates to a power supply, and especially relates to a power supply avoiding an auxiliary boost circuit over voltage.
2. Description of the Related Art
When a related art alternating current power supply apparatus stops supplying an alternating current power to a related art power supply, an output voltage of the related art power supply will not drop to zero volt immediately. The output voltage will drop to zero volt gradually, so that a direct current to direct current converting circuit of the related art power supply and a load apparatus are protected. However, the direct current to direct current converting circuit may be still damaged by the variation of the output voltage. Therefore, the components in the direct current to direct current converting circuit must have high specifications (for example, high voltage resistance), so that the cost of the direct current to direct current converting circuit is increased.